The goal of the project is to synthesize bifunctional ligands which have a high affinity for Pb(II) and Bi(III) by virtue of the presence of sulfur donor atoms. Simple thiolate ligands such as dimercaptosuccinic acid have been shown to form complexes of high stability with both ions (Kf for the 1:2 Bi:DMSA complex is log 43.87), yet appropriate multidentate chelating agents suitable for linkage to monoclonal antibody are not yet available. We intend to systematically explore this chemistry by incorporating thiol donor atoms into both acyclic and cyclic chelating agents. Appropriate precursor molecules have been synthesized which will allow us to test methodology for the incorporation of thiols into new chelating agents.